La Jornada: They identify a wild relative of the chayote; will allow us to reconstruct its evolutionary history

Boiled, steamed or stewed, chayote is a staple in Mexican cuisine, along with corn and zucchini. However, few wonder where it comes from: has it always been like this or did it have a different “ancestor”?

To answer it, a team from the Institute of Ecology of the National Autonomous University of Mexico (UNAM) in collaboration with the Natural Resources Laboratory at the Faculty of Higher Studies of Iztacala took on the task of tracing its origin.

In the study published in the scientific journal Molecular Phylogenetics and Evolutionresearchers confirmed – with genetic evidence – that the chayote that we consume today was domesticated in southern Mexico, in the so-called biogeographic province of Oaxaca, which covers parts of Oaxaca, Puebla and Veracruz. Furthermore, through DNA analysis they precisely identified their closest wild relative, allowing their evolutionary history to be reconstructed.

“Family tree”

But one of the most relevant findings of the work, led by Cécile Truchot Taillefer, a doctoral student at the UNAM Institute of Ecology, was the low genetic diversity and small size of wild populations, which raised alarms among scientists due to their vulnerability to the continued loss of tropical cloud forests.

For this work, the researchers sequenced the DNA of 79 plants, both cultivated and wild, and analyzed thousands of genetic variations – known as SNPs –, which allowed them to reconstruct their “family tree.”

In interview with The DayRafael Lira Saade, attached to the Natural Resources Laboratory at the Faculty of Higher Studies of Iztacala, explained that all the plants we consume come from a wild relative. He highlighted that the link between the cultivated and the wild is the bridge between what we eat today and what we can eat tomorrow.

He added that wild relatives tend to have greater genetic diversity, allowing them to resist pests, tolerate drought and adapt to climate changes. In that sense, preserving them is key in the case of chayote, whose seed is particularly fragile and difficult to preserve.

“You can preserve pumpkins if you keep their seeds, but in the case of chayote, it has only one seed and it is very weak; if you freeze it, it dies, if you keep it alive, it sprouts,” he noted.

Due to climate projections for 2060 that predict a total loss of suitable habitat for their closest wild relatives, Erika Aguirre Planter, from the Laboratory of Molecular and Experimental Evolution of the Institute of Ecology, who also participates in this project, spoke out in favor of protecting them.

He proposed that they should be included in national protection lists, such as the Official Mexican Standard NOM-059, and international ones, such as the IUCN Red List. They considered that such inclusion would guarantee their legal recognition and institutional protection.

The researchers warned that wild relatives are not only key to understanding the origin of crops, but also represent an indispensable genetic reserve to face agricultural challenges. Its loss, they point out, could limit the ability to develop more resistant plants and put food security at risk.

“If we no longer have those genetic resources from wild relatives, our response capacity is reduced,” warned Lira Saade. “Chayote is an example, but the same thing happens with fundamental crops like corn or wheat, and the consequences can be very serious.”

In this sense, Truchot Taillefer stressed the importance of knowing these species, locating the regions where they live and becoming aware of their conservation. “We have to take care of the plants, not only the wild relatives of the chayote, but nature in general,” he concluded.